• Transactions of the Korean Society of Machine Tool Engineers
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• 제10권1호
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• pp.65-70
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• 2001

The hear transfer mechanism initiating the friction welding is examined and a transient three dimensional heat conduc-tion model for the welding of two dissimilar cylindrical metal bars is investigated. The cylindrical metal bars are made of materials made of A2024 and SM 45C. Numerical simulations of heat flow are performed using the finite volume method. Respectively. Commercial FLUENT code is used in the heat flow simulation and maximum temperature and distribution of temperature are calculated. Temperature of friction welded joining face is compared with the temperature distribution measured by experiment and numerical simulation. The maximum temperature of friction welded joining face is lower than melting point of A2024-T6 aluminum alloy using insert metal. The temperature distribution of friction welded join- ing face with insert metal is more uniform than that of without inset metal.

• Journal of the Korean Ceramic Society
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• 제35권8호
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• pp.791-794
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• 1998

• Proceedings of the Korean Society of Precision Engineering Conference
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.196-202
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• 1997

A reinforced hydraulic hoses,caiied a resonator hoses,with fixible metal tube are commonly used in automotive power steering hydraulic systems to attenuate and eliminate the objectionable fluid borne noise(pressure ripple) or vibration produced by a pump or steering gear. To achieve better nose attenuation in automotile vehicles, the investigations on propagation and attenuation characteristics of fluid borne pressure ripple in power steering hydraulic ciruit are required. So, this paper descibes a mathematical model of hydraulic hoses to support design the power steering hydraulic circuit and analyze the attenuation characteristics of flow and pressure ripples. The model is based on the transfer matrix approach. The experimental results show that the pulsation attenuation characteristics of hydraulic house is remarkably affected by the flexible metal tube inserted coaxially inside a hydraulic hose with a finite length as well as viscoelastic properties of house wall. It is also shown that the predicted results bymodel proposed here agree well with the measured results over a wide frequency range. These results will assist in the modeling and design of hydraulic hoses, and hear, should provide a means for designing a quieter automotive power steering hydraulic systems.

• Korean Journal of Organic Agriculture
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• 제9권3호
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• pp.85-92
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• 2001

The effect of Dolichos lablab leave extract on enzyme activities in mice blood was investigated in this study to clarify the new useful application of the Plant leaves. There were not significant differences in the enzyme activities in mice blood among treatment fed with the leave extract and non fed control. The feeding treatment with the extract showed a tendency to activity compared to the nun fed control. The activities of glutamate oxaloacetate transaminase, glutamate pyruvate transaminase and lactate dehydrogenase in mice blood at the treatment fed with lead and the leave extract were significantly low compared to their activities at the non fed treatment with the extract, respectively. The choline esterase activity was high at the leave extract feeding. The cadmium dietary treatment showed the same result as the lead treatment. In conclusion, the physiological function of the Jebikong leave was significantly in creased when the mice was stressed by the hear metal intake. Therefore, the plant leave extract would consider the reduction of heart metal effect.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 한국공작기계학회 2003년도 추계학술대회
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• pp.289-294
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• 2003

The object of this study is to investigate the effect of compounded welding by using acoustic emission (AE) signals fur weld heat affected zone (HAZ) in tensile testing. This study was carried out a SM 490A high tension steel for electronic shielded metal are welding (SMAW), $\textrm{CO}_2$ gas arc welding and TIG welding. And correspondingly, the root openings are 3, 4 and 2.8mm. Data displays are based on the measured parameters of the AE signals, along with environmental variables such as time and load. These history plots give us useful and powerful information to analyze the results of material evaluation testing.

• Journal of environmental and Sanitary engineering
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• 제16권3호
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• pp.80-86
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• 2001

This research was carried out to investigate the effect of microscopic silica matrix coagulation on heavy metals and anion removal in mining wastewater. pH and alkalinity played an important role to coagulate heavy metals such as Al, and Fe and an anion such as ${SO_4}^{2-}$ with silica matrix as well as NaOH. However, the efficiency to form coagulates was much greater in silica matrix-treated wastewater than NaOH-treated one. Fe in wastewater formed coagulation with both silica matrix and NaOH treatments resulting in lowering Fe content in wastewater at above pH 9. For Al removal in wastewater, silica matrix-treated wastewater at above pH 12.3 formed stable coagulate with Al, while NaOH-treated one did not. Alkalinities of 89 and 220 mg/L were required to stabilize silica matrix treated coagulate with Fe and Al, respectively. Reaction time of ten minute was required to provide enough reaction for coagulation between heavy metals and silica matrix. Heavy metals and anion leachates were much lower in coagulate with silica matrix than that with NaOH, which indicates that silica matrix could be used to remove heavy metals efficiently.

• Korean Journal of Fisheries and Aquatic Sciences
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• 제36권1호
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• pp.55-61
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• 2003

This study was conducted to evaluate distribution and behavior characteristics of heavy metals for tidal flat sediments in the Saemankeum area. The value of heavy metal contents in the tidal flat sediments were higher than that surveyed in 1994, but showing that it's lower when compared with the value of Shiwha lake. Enrichment factors in the tidal flat sediments showed below 1 except for Pb and Zn. Metal excesses was appeared that Cu, Cr, Fe, Mn lacked and Pb, Zn were high. The correlation analysis between heavy metals and organic matters was found high positive relationship (r=0.424$\~$0.839), especially correlation coefficient between ignition loss and oxide Al, Fe, Mn showed high positive relationship above 0.7. The correlation analysis between Brain size and hear metals was found that as grain size was small, heavy metals contents were increased. Correlation coefficient between silt and heavy metals except for Cu, Pb showed high positive relationship as 0.552$\~$0.732.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 한국항해항만학회 2005년도 춘계학술대회 논문집
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• pp.311-316
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• 2005

A laboratory study on the adsorption of nitrate contaminated in nearshore water using various materials including several types of dredged sediments(ST) and yellow clays(YC), which are activated by hear(HT), bioleaching for heavy metal removal(BL) and neutralization(NR) was performed. The equilibrium time of the adsorption for the sediment bioleached and treated by heat(BL-HT-ST) was only 17min. which was faster than the sediment bioleached, neutralized and treated by heat(BL-NR-HT-S) (25min) or the sediment treated by the bioleaching process(BL-ST)(27min), but longer equilibrium times for yellow clay(YC) or heat treated yello clay(HT-YC) were required. The adsorption processes of nitrate in sea water for tested material could be described by Freundlich isotherm, but were significantly affected by surface characteristics of the materials. The adsorption capacities for raw sediment and heat treated sediment were 2.12, 2.19mg $NO_{3}$-N/g, respectively, which were higher than others, indicating that the sediment activated by heat could be used as a material for the improvement of nearshore water quality.

• Journal of Korean Society of Forest Science
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• 제84권3호
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• pp.286-298
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• 1995

This study was carried out to investigate the effect of forest soil acidification on the distribution of exchangeable cations($Ca^{2+}$, $Mg^{2+}$, $Al^{3+}$) and heavy metals(Cu, Zn, Mn, Pb, Cd) in soil, and to understand the relation of the soil chemical properties and the distribution of nutrients and hear metals in fine root and foliage. The results through survey on the long - term change of soil pH and the contents of nutrient and heavy metal in soil, fine root and foliage by 2 sites near Ulsan - Onsan industrial estate and 2 sites in limited development district are summarized as follows : 1. The average forest soil pH(A horizon) in Ulsan had been proceeded down to 3.73 in deciduous forest and 3.86 in coniferous forest in 1994 from 4.45 and 4.78 in 1987, respectively, which indicated serious soil acidification. As comparing soil pH among sites, Dongcheon coniferous forest(pH 4.57) in limited development district showed the highest values and Dangwol deciduous forest(pH 3.19) near Onsan industrial estate showed the lowest values in 1994. 2. Contents of exchangeable calcium in forest soils of limited development district where showed much higher soil pH than industrial estate were 3.5 times more in deciduous forest soil and 11 times more in coniferous forest soil than in industrial estate, and contents of exchangeable magnesium were also 4.5 and 5 times more in limited development district than in industrial estate, respectively. However contents of exchangeable aluminium which had been supposed more in forest soil of industrial estate were more in limited development district. 3. Contents of calcium and magnesium in fine root of deciduous trees(A hirsuta. Q. acutissima) were 3.6 and 1.7 times more in limited development district than in industrial estate, respectively, and those of coniferous trees(P. rigida, P. thunbergii) were 4.6 and 1.5 times more in Limited development district than in industrial estate, respectively. Also contents of calcium and magnesium in foliage of deciduous trees were 1.1 and 2.2 times more in limited development district than in industrial estate, respectively, and those of coniferous trees were 1.8 and 3.3 times more in limited development district, respectively. And contents of aluminium in fine root and foliage were nearly as same as in soil. 4. Ca/Al molar ratios in soil and fine root, which could be related with the dgree of soil acidification and Al toxicity on trees, were Less than 1 in all sites except Dongcheon, suggesting that the soil and fine root in the sites have high sensitivity to soil acidification and the decrease in nutrient uptake and root enlargement. The Ca/Al molar ratios in soil and fine root in coniferous forest were highly correlated with the soil pH one another. 5. Contents of Cu, Zn and Pb in soil, fine root and foliage were more in industrial estate than in limited development district in both deciduous and coniferous forests, however, oppositely contents of Mn and Cd in soil were more in limited development district than in industrial estate.